CVE-2023-21270: App Retains Unauthorized Permissions in PermissionManagerServiceImpl.java

A recent vulnerability has been discovered with the CVE-2023-21270 identifier, affecting the Android operating system. An application can exploit this vulnerability to retain permissions during an update that should have been revoked. Since user interaction is not required for exploitation, threat actors can potentially abuse this vulnerability, leading to local escalation of privilege attacks.

In this post, we will delve into the details of this security vulnerability, analyze the affected code snippet, provide relevant links to original references, and discuss potential implications and fixes.

CVE-2023-21270: Explained
The core issue resides in the restorePermissionState() method within the file PermissionManagerServiceImpl.java. During an app update, an incorrect set of permission flags is cleared, allowing the application to retain permissions that should be revoked. This enables threat actors to perform local escalation of privilege attacks.

Incorrect behavior is present in the method restorePermissionState() as shown below

@Override
public void restorePermissionState(String packageName, int userId, boolean grantedOnly) {

    // ... code removed for brevity

    synchronized (mLock) {
        final Set<String> oldRequestedPermissions = s.getRequestedPermissions(userId);
        final PermissionsState permissionsState = s.getPermissionsState();

        for (String permissionName : permissions) {
            Permission permission = mRegistry.getPermission(permissionName);
            if (permission == null) {
                continue;
            }

            final boolean hadPermission = permissionsState.hasInstallPermission(permission.info);
            final boolean shouldGrantPermission =
                    (!grantedOnly || oldRequestedPermissions.contains(permissionName))
                            && !permissionsState.isPermission(permission.info,
                            PackageManager.FLAG_PERMISSION_RESTRICTION_UPGRADE_ONLY);

            if (hadPermission && !shouldGrantPermission) {
                // Incorrect permission flag got cleared; should have revoked permission
                s.revokeRuntimePermission(permission, userId);
            } else if (!hadPermission && shouldGrantPermission) {
                permissionsState.grantInstallPermission(permission);
            }
        }
    }
}

Original References

- Android Security Bulletin CVE-2023-21270
- Android Open Source Project (AOSP)
- PermissionManagerServiceImpl.java

Exploit Details

The local escalation of privilege vulnerability allows a malicious app to perform nefarious activities, such as unauthorized data access or theft, system compromise, or malicious actions execution while retaining the higher privileges. This can happen even when the user has not explicitly granted the permissions.

This vulnerability impacts devices running on affected Android versions, granting the app execution privileges even though user interaction is not required for exploits.

Potential Fix

The potential fix for CVE-2023-21270 is to ensure that the restorePermissionState() method correctly revokes the permissions during the app update process.

Conclusion

CVE-2023-21270 is a critical vulnerability in Android's permission management system that can lead to local escalation of privilege attacks. Developers and users must be vigilant in patching their systems and incorporating security updates to protect against the potential exploitation of this issue. Regularly auditing and analyzing your app's permissions can help ensure that it only has access to crucial and user-approved resources. Additionally, staying informed on the latest security bulletins and best practices will help you proactively protect your data and systems.

Timeline

Published on: 11/19/2024 18:15:19 UTC
Last modified on: 11/20/2024 17:35:18 UTC